Booster pumps



H. E. ADAMS 3,080,823

BOOSTER PUMPS sheets-sheet 1 March 12, 1963 Original Filed Nov. 15, 1951March 12, v1963 H. E. ADAMS 3,080,823

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BYMIM*M Unite States This invention relates to booster pumps,particularly fuel booster pumps for aircraft engines. The novel fuel-booster pump of the present application is particularly designed to beused in the fuel line between a tank mounted booster pump and the mainfuel pump of the engine, but is also adapted for other uses. The novelpump is desirably like the combined centrifugal and Vacuum pumpsdisclosed in United States Patent No. 2,461,865, and in my applicationSerial No. 652,633, now Patent No. 2,581,828, tiled March 7, 1946, forPumps, but embodies further improvements especially adapted to meet theexacting requirements of line mounted booster pumps.

This application is a division of application Serial No. 256,580, filedNovember 15, 1951, now Patent No. 2,956,- 504,

Because of the increased capacity required of the main engine fuel pumpof an aircraft engine, it has become necessary to increase the pressureof liquid supplied to the inlet of this pump in order to preventcavitation and vapor locking within the pump inlet passages. Thispressurization has been furnished by a centrifugual booster pump mountedin the fuel tank, by pressurizing the tank, o1', in some instances, byan auxiliary line mounted posi tive type fuel booster pump. Y

With the still greater increase in fuel requirements of the present-dayaircraft engine, particularly of the gas turbine type engine, there havedeveloped increased pressure losses in the fuel line between the fueltank and the main engine pump inlet, together with an increased pressurerequirement at the main engine pump inlet because of the greatercapacity of the latter pump. Both of these factors have imposed thenecessity that constantly higher pressures and ows be supplied by thetank mounted booster pump. This, in turn, has increased the weight ofthe required tank mounted pump, and has also increased the driving powerrequired therefor.

All these requirements tend to approach or exceed the practical limitsof weight and available electric power for booster pumps. The mainengine fuel pump must be increased in size, which seems impractical, or,as disclosed herein, it may be supplemented by a line booster pumpdriven directly by the engine and mounted on the engine itself topressurize its own main fuel pump.

The engine mounted line booster pump does not do away with the tankmounted booster pump. It merely reduces the discharge requirement fromthe tank mounted booster pump. The tank mounted booster is necessary forthe prevention of vapor locked in the fuel lines, even when the enginedriven booster pump is present.

The line' mounted booster pump is required to deal with conditions4 ofconsiderably greater severity than those encountered in the operation ofa tank mounted booster pump.

When the fuel in a tank is caused to vaporize or boil because of thereduced ambient absolute pressure as the aircraft climbs, it is ditcultto pump. Under such conditions, either the fuel supply tank must bepressurized to bring the absolute pressure' in the tank above the vaporpressure of the fuel, or, if the tank is vented to the atmosphere,resort must be had to a tank mounted fuel booster pump capable ofhandling this boiling fuel, as disclosed 1 arent' "ice for example inPatentV No. 2,461,865 and Serial No. 652,- 633, now Patent No.2,581,828.

Although, in the fuel tank the Iwholel body of fuel is boiling, most ofthe vapors escape to` the free surface. at the top of the tank and passout through the vent. Only a very small proportion of the vapor is drawnthrough the inlet of the pump from the tank. The tank mounted pump,therefore, is required to handle only a smallrproportion of the vaporsgiven off by the fuel in the tank.

In the case of ak fuel line, however, supplying fuel to the pump, noneof the vapor that is released from `the time the fuel leaves the tankuntil its reaches the. pump suction can escape. The whole mixture iscarried on by the velocity of the fuel in the line to the inlet of thepump, where all of the vapors evolved from the fuelmust be handled bythe pump, if pumping is to continue.

ln the line there is a friction loss, and consequently a pressure drop,between the point where fuel leaves the tank and where it enters theinlet of the line booster pump. This reduction is pressure, due tofrictional resistance, reduces the absolute pressure of the fuel trappedin the line below the fuel vapor pressure, causing vapors to be evolvedin the line all of the which vapors must be handled by the pump. Thus,the problem of pumping boiling liquids in an enclosed suction line isconsiderably more dillicult than that of pumping liquids from a tank.

Where relatively small tlows have been involved with resultant lowerpressure drops, positive type line booster pumps such as vane or gearpumps have been successfully used. These pumps have to be proportioned,however, so that they will handle a total displacement equal to theliquid fuel to be handled, plus the vapors given ofi` by the fuel in itstravel from the tank to the entrance of the positive type booster pump.l

With the increase in flow rate and resulting increased pressure drop,together with the increased volatility of aircraft turbine fuels, theproportion of vapor to liquid has grown to such an extent as to makeimpracticable the employment of positive type booster pumps. In otherwords, the size and weight of the required pump would be prohibitive.

It is well known, of course, that a centrifugal pump will handleconsiderably larger volume for pump weight than will a positive typepump, but it is also well known that a conventional centrifugal pump forliquid is extremely sensitive to the presence of gas or vapor, and thatits pumping action will break down when the gas or vapor componentconstitutes more than three percent by volume of the mixed fluid to behandled.

A combined centrifugal and vacuum pump of the type as exemplified inPatent #2,461,865 and Serial No. 652,- 633, now Patent No. 2,581,828,has unique provision for the separation, removal and recompression oflthe vapors. It has been found that this type of pump can be used onpipe line applications by increasing the separating proportions of theliquid pump and increasing the vapor handling proportions of the vacuumpump or compressor, and tnen returning the recompressed vapors to thefuel tank. This type of pump is now being extensively used as an enginedriven booster pump in the manner referred to.

ln the simplest engine driven line booster pump of this kind, the vaporsare returned by a separate pipe line back to the fuel tank from whichthey started, or to some other fuel tank. The vapor removing andcompressing element in sending the removed vapors back to the tank hasto pressurize the gases and vapors sufficiently to overcome pipefriction and any static head difference between the pump and thereceiving tank. This pressure difference, though greater than has to bemaintained in the case of the tank mounted fuel booster pump, is stillrelatively low.

It is not always convenient to return the removed gases and vapors to afuel taink, however, in which case the only place for the vapors to bedischarged would be to the -line that carries the liquid discharged bythe booster pump to the main fuel pump inlet. Because of the higherintermediate pressure between the line booster -pump discharge and themain fuel pump inlet, the vapors removed from the suction side of thebooster pump would have to be compressed sufficiently to cause them tobe substantially completely recondensed. Any uncondensed vapor residueand any uncondensable gases would be so small involume, however, becauseof the high pressure, as to have no substantial adverse effect upon themain fuel pump. The compression of these vapors from the booster pumpinlet absolute pressure to the booster pump outlet absolute pressure, ofcourse, requires greater power because of the greater pressuredifference, as compared with the pressure differential required todeliver these same vapors back to the fuel tank.

It is a primary object of the present invention -to provide a liquidbooster pump in combination with a compressor capable of drawing off thevapor and gases at the intake side of the pump, and of recompressingthem suciently to adm-it of their recombination with Vthe liquid at thedischarge side of the pump.

It is a more specific object to provide a centrifugal liquid pumpcapable of separating entrained gas and vapor from the liquid, togetherwith a compressor of the hydroturbine type driven in unison with theliquid pump and arranged to draw off the vapor and gas from the intakeside of the liquid pump, to compress the gas, compress and recondensethe vapor, and then to combine its output with the liquid pump output.

To this end it is a feature, in accordance with one practical andadvantageous embodiment of the invention,` that the discharge pressureof the compressor is made at least equal to that of the liquid pump bymaking the rotor diameter of the compressor approximately the same asthe impeller diameter of the liquid pump.

It is necessary that the centrifugal liquid pump be designed to give therequired full pressure at low engine speeds. When the engine isoperating at normal speed, the centrifugal liquid pump, therefore, isgenerating a much higher pressure than is required. This is because ofthe well known characteristic of centrifugal pumps lthat the pressuregenerated varies as the square of the rotational speed, whereas capacityvaries as the first power of the rotational speed. These samecharacteristics are inherent in the hydroturbine vacuum pump orcompressor. During normal operation of the engine, therefore, both thecentrifugal liquid pump and the compressor of the combination referredto in the preceding paragraph would be operating to deliver considerablyhigher pressures than are actually necessary. In the case of someaircraft or gas turbine fuel systems, it is desirable to maintain thenatural pressure of the main engine fuel pump at some regulatedpressure. Where booster pumps are used which generate wide variations inpressure because of variations yin speed, it has -been the practice tointerpose some form of regulating valve to maintain the desired inletpressure to Vthe main engine fuel pump.

As the engine speed is decreased toward idling speed, the required vaporand liquid can be also'decreased. Because of the characteristics of thefuel system, the fric-tional drop in the inlet piping diminishes rapidlywith the reduced liquid flow, so that the vapors required -to be handledby the compressor decrease even out of proportion with the decreasedrotational speed. If, therefore, the compressor is made adequate to meetthe vapor handling requirements at the normal operating speed of theengine, and adequate to furnish the pressure required at the inlet ofthe main engine fuel pump at that speed, the necessity for making thecompressor capable of delivering the same pressure as the associatedliquid pump may be avoided by throttling down the discharge pressure ofthe liquid pump to the required inlet pressure of the main fuel pump,and combining the compressor output with the liquid pump output onlyafter the latter has been throttled down.

It is accordingly a further feature, in accordance with anotherpractical and advantageous embodiment of the invention, that thecompressor, though constructed to produce a lower discharge pressurethan the liquid pump, is enabled to combine its output with that of theliquid pump by providing a liquid pressure reducing valve at thedischarge side of the liquid pump.

It is a still further feature that a combined liquid pump and compressorunit is provided, capable of handling the gas and vapor on the one handand the liquid, on the other, in the compressor and the liquid pumprespectively, and of recombining the pump and compressor outputs, butfurther adapting for convenient alteration to divert the compressed gasand vapor back to the source of liquid supply in any organization inwhich such diversion is deemed preferable.

Other objects and advantages will hereinafter appear.

In the drawing forming part of this specification.

FIG. l is a longitudinal sectional view of a combined line pump andcompressor embodying one form of the invention, the section being takenupon the line 1 1 of FIG. 4 looking in the direction of the arrows;

FIG. 2 is a fragmentary, longitudinal sectional view of the samestructure, the section being taken upon the line 2 2 of FIG. 4 lookingin the direction of the arrows;

FIG. 3 is a further longitudinal sectional view of the same structure,the section being taken upon the line 3 3 of FIG. 4 looking in thedirection of the arrows;

FIG. 4 is a transverse sectional view taken upon the line 4 4 of FIG. llooking in the direction of the arrows;

FIG. 4a is a transverse sectional view through the compressor, thesection being taken upon the line 4ta-4a of FIG. 1, looking in thedirection of the arrows;

FIG. 5 is a View in side elevation of a portion of the pump casing witha cover plate removed;

FIG. 6 is a view of one of two alternative cover plates adapted to beapplied to the complementary portion of the casing member shown in FIG.5 when the compressed gas and vapor are to be returned to a fuel tank;

FIG. 7 is a view of an alternative cover plate which is substituted whenthe compressed gas and vapor are recombined with the liquid en route tothe main fuel pump;

FIG. 8 is a fragmentary sectional view similar to FIG. 2, butillustrating a modified pump and compressor combination in which thecompressor is capable of delivering as high a discharge pressure as thecentrifugal liquid pump;

FIG. 9 is a longitudinal sectional view of a duplex liquid pump andcompressor combination in which a single cornpressor serves both workingchambers of the liquid pump, the section being taken upon the line 9 9of FIG. l0 looking in the direction of the arrows;

FIG. l0 is an end view, partly broken away, of the pump and compressorcombination of FIG. 9, the planes of the portions shown in section beingsubstantially indicated by the line 0 10 of FIG. 9, looking in thedirection of the arrows;

FIG. ll is a fragmentary sectional View taken upon the line Il lli ofFIG. 10, looking in the direction of the arrows; and

FIG. 12 is a fragmentary sectional view taken upon the line 12 l2 ofFIG. l0, looking in the direction of the arrows.

The illustrative pump and compressor unit of FIGURES l to 7 comprises acasing which consists chiefly of complementary casing members 2 and 3having flanges 4 and 5, respectivelypthrough which they are secured toone another in axial alignment by machine screws 6. The casing member 3is provided with threaded bores '7 which are adapted to receive thethreaded bodies of headed screws (not shown) for clamping the casingupon a flanged fuel supply pipe section (not shown) in axial alignmenttherewith.

The unit 1 includes .liquid iinpeller blades 8 and compresser rotorblades 9, both of which are desirably made integral with a driving disc10. A flange 12 of the disc lil is revolubly received within an annularilange 13 which forms part of a stationary compressor body member 14.

An annular groove 1l is formed in the body member 14 and forms part of aseal chamber between the liquid end and the vapor end of theimpeller-rotor. This chamber is connected to the interior of the liquidimpeller passageways by a bore 11x, to avoid the building up ofexcessive pressure between the impeller shroud and thev lobe seal andthereby to avoid ooding of the vapor pump.

The disc 1t? is secured upon a driving shaft 1S to be driven in unisonwith the shaft by means of a key 16. The hub of the disc is secured upona reduced portion 17 of the shaft 15. The left hand hub face of the disc1G (as viewed in FIGURE l) bears against a washer 18, which washer inturn bears against a shoulder 19 of the shaft 15.` A second washer 20'bears against the right hand hub face of the disc 10, being pressedagainst the disc by a nut 21 which is threaded onto a further reducedend portion 22 of the shaft 15.

The driving, bearing and sealing details of the shaft 15 form `no partof the present invention. Brielly, the intermediate portion of the shaftis supported in a stationary bearing 23. A sylphon bellows 24 sealed tothe shaft 15 through its head 25 at one end, carries at its opposite enda bearing ring 26 which is pressed by the bellows into bearingengagement with an end face of the bearing 23.

An enlarged portion 27 of the shaft 15 carries the inner race 28 of aball bearing 29, the outer race 3i? of which is secured in a cup portion31 of the casing member 2. The shaft 15 is adapted to be connected to anengine-driven shaft (not shown) through a splined coupling, the shaftbeing formed with a splined end 35 for mating with a complementaryrecess of the engine driving shaft.

The compressor body member 14 is formed interiorly to provide twoopposed eccentric lobes 33 and 34. As is well understood, the rotorblades 9 divide the rotor into compartments or buckets, and serve todrive a ring of liquid, in the illustrative case liquid fuel, around inthe casing. Since the liquid is thus subjected to centrifugal force, itrecedes from the center of rotation as the lobe depth increases and isforced back toward the center by the outer lobe wall as the lobe depthdiminishes. The outer boundary of the ring always coincides with theinner wall of the casing 14. The inner boundary or the ring is indicatedby the dot and dash line 14e of FIG. 4a. A pocket is alternatelyexpanded and contractedat the inner end of each bucket or compartment ofthe rotor during the traverse by the bucket of each of the lobes, vaporbeing caused to be drawn into the bucket through an intake port 36formed in a stationary central cone 37 as the liquid moves outward ,andbeing compressed and driven from the bucket through an outlet port 38 ofthe cone 37 as the liquid moves inward. Since the traverse of a singlelobe completes the pumping cycle for each bucket, two dit-.metricallyopposed inlet ports 36 and two diametrically opposed outlet ports 38 areprovided in the cone 37, so that each lobe has an inlet port and anoutlet port associated with it.

The cone 37 forms an integral part of a stationary head section 39 whichhas passages 4i) therein that communicate with the ports 36, andpassages 41 therein that communicate with the ports 38. The left handface of the head section 39 is generally open and is covered by a porteddisc 42. The casing member 2 carries the body member 14, the head member39, and the ported disc 42.

Body member 14 is composed of the annular ring 13, lobes 33 and 34, headsection 39 and ported disc 42, which are all formed into one inte-gralpart by furnace brazing. Studs 43 are passed through the casing member2, and have reduced ends threaded into the ring portion 13 ofthe bodymember 14. Nuts 45' are threaded onto the studs 43 for holding the bodymembers 2 and 14 together.

Dowel pins 46 are passed through the disc 42 and the head member 39 andinto the annular ring 13 for maintaining the alignment and orientationof these parts during the brazing process. y

The casing member 2 is provided with vapor inlet passages 47 and withvapor outlet passages 48 which com municate respectively with the inletpassages 40 and the outlet passages 41 of the head member 39. T he'passages 47 and 48 also communicate with inlet and discharge passages 49and 50, respectively, which are formed in the casing member 3.

The liquid fuel, with its entraine'd vapor, enters the eye oftheimpeller a`t51. As explained in Serial No. 652,633, now Patent No.2,581,828, the liquid pump is especially designed to cause the gas andvapor to be separated from the liquid and to becollected in an annularchannel 52 which isformed inthe liquid pumping chamber of the casingmember 3. The vapor and gas are sucked out from the channel 52 throughbores 52x and 53, a channel section 54 formed in the casing member 3, achannel section 55 formed jointly in the casing member 3 and a coverplate S6, and thence through the passages 49, 47 and 40 to the pumpingchamber of the compressor.

v The liquid fuel is freed of entrained gas and vapor by the'cornbinedaction ofthe liquid pump and the compressor, and is then dischargedthrough a volute passage 57 to a discharge conduit 58. In passing fromthe passage 57 to the conduit 5S, the liquid automatically has itspressure reduced by reducing valve mechanism 59 to substantially apredetermined gaugeI pressure regardless of the speed at which theengine is operating. The valve mechanism is mounted in the conduit 58,being carried by a supporting plate 6i). The plate Gil is detachablysecured along with a cover plate 61 to the portion of casing 3 whichforms an end of the conduit 58 by machine screws 62.

The plate 60 is connected in sealed relation to one end of a corrugatedbellows wall 63. The opposite end of the bellows wall is connected to amovable valve body 64 which is composed of complementary members 65 and66. The bellows is closed at its forward end by the piston, but thebellows is open at its rear end and communicates with the atmospherethrough passages 67, 68, 69, 70, 71, 72 and a vertical drain tapping 72xat the bottom of casing member 2.

The valve body 64 slides in a cylindrical member 73 which is iixed inthe conduit 58. The liquid fuel discharged from the volute passage 57enters a circumferential channel 74 of the valve formed externally ofthe valve body, through an opening 75 which is provided in the'cylindrical member 73. The channel 74 normally extends to the left ofthe cylindrical member 73 and cornmunicates through openings 76 with theconduit 58. A stop shoulder 77 stands in the way of the valve body 64 tolimit inward movement of the valve and prevent overextension of thebellows 63. The end of the adjusting screw 80 stands in the way of thevalve to limit outward movement of the valve and thereby preventover-compression of the bellows.

A compression coil spring 78 bears at one end against the valve body 64and at the opposite end against a hanged and shouldered nut 79. The nutis threaded on the screw Si) which is mounted on the plate 61 withcapacity for ro tation, but not for axial movement. The screw is formedwith a flange 81 which engages' the inner face of the plate 61. A neckand head portion 82 of the screw extends through the plate 61, theprotruding portion of the head being slotted. A boss 83 on the face ofplate 61 is slotted to provide a means of locking screw Sil withlockwire 84.

The flange of nut 79 has a llat face which bears against a dat sidedlinger 85 that extends inward from the plate 61. The linger 85 preventsrotation of the nut 79. As ,the screw 89 is turned by the head 82,therefore, the iiut 79 is prevented from turning, and hence is caused tobe fed axially along thescrew in one direction or 7 the other accordingto the direction in which the'screw is turned.

Liquid will ow from the volute passage 57 through the valve channel 74and into the conduit 58 so long as the valve body is not moved farenough to the right to close the openings 76 completely. Duringoperation, pressure of the liquid in the conduit 58 tends to move thevalve body or piston 64 toward the right, and this is opposed byatmospheric pressure acting within the bellows and the pressure of thespring 78 bearing leftward against the piston. The absolute pressure inthe conduit S, therefore, will generally be substantially atmosphericpressure plus a predetermined amount which depends in value upon theadjustment of the nut 79. When the nut 79 is adjusted toward the left,the resistance of the spring 78 which will have to be overcome prior tocut off, is increased, and when the nut 79 is adjusted toward the right,the resistance of the spring 78, which will have to be overcome prior tocut off, is reduced. The former adjustment increases the gauge pressurewithin the conduit while the latter adjustment reduces the gaugepressure within the conduit.

There is a passageway 79a leading fromv the chamber beyond the dischargevalve, back to the pump suction. The purpose of this passageway is tobleed oif some of the fuel beyond the discharge valve chamber back tothe pump suction for the purpose of better regulation of the dischargepressure. By continuously bleeding of a slight amount of the fuel, thepressure is prevented from reaching undesirable limits when the controlvalve itself is closed and has done all of the regulating it can.

There is some liquid which is discharged by the vapor pump beyond thecontrol valve and at times of operation where the control valve isclosed, the discharge pressure developed by the vapor pump may be toohigh for the engine fuel system. By bleeding olf this small amount ofliquid, the ultimate discharge pressure is prevented from going to toohigh a limit.

Because of the pressure reduction effected by the valve 59, thecompressor itself can operate at a lower discharge pressure than wouldotherwise he necessary if it were required to discharge against the fullcentrifugal pump pressure. The purpose of this valve is primarily forregulation of the fuel pressure and advantage is taken, as long as thevalve is required in the circuit, to discharge the vapors to the reducedpressure.

The aircraft designer may cause the compressed gas and vapor to bedischarged into the conduit 58 which leads forward to the inlet of themain engine pump, or to be returned to a fuel tank, whichever is moreconvenient.

If the compressor output is to be returned to a fuel tank, the coverplate 56, as shown in FIGURES 4 and 6, is applied to the casing member3. The upper and lower halves of the plate 56 are divided from oneanother by a horizontal partition 87 which divides a lower pocket SSfrom upper pockets S9 and 90. The partition S7 coincides with apartition wall 91 of the casing member 3. The upper pockets 89 and 90are divided from one another by a vertical imperforate partition 92which coincides with a partition wall 93 of the casing member 3. Thelower pocket 38 forms a part of the conduit section 55 through whichcommunication is established between the groove S2 of the centrifugalliquid pump and the intake side of the compressor, as

A already described.

vapor forward through the conduit 58, however, a cover plate 56a is usedin place of the cover plate 56, and the plug 94 is secured in place, asshown in FIGURE 2. The plate 56a is like the plate 56, being providedwith partitions 87a and 92a which divide the inner side of the plateinto pockets 88a, 89a and 99a. The only difference between the twoplates resides in the fact that the parti- Iion 92a has a bore 95 formedin it for placing the pockets 89a and 90a in communication with oneanother. This places the pocket 39a in communication with the outletpassage Si? of the compressor. The pocket 89a always communicatesdirectly with the conduit 53 and hence transmits the products from thecompressor into the conduit 58. IIn this case the plug 94, rather than atube is applied to the interiorly threaded end of the passage 50.

The plates 56 and 56a are not necessarily mutually distinct structures.'The plate 56 may be converted to the plate 56a simply by making a bore95 through the partition 92. The plate 55a may be converted back to theplate 56 by plugging the bore with a bolt 95a.

The pump of FIGURE S differs from the pump of FIGURES l to 7 primarilyin the fact that the discharge pressure of the compressor is caused tobe at least as great as the unthrottled output pressure of thecentrifugal pump, so that no throttling of the centrifugal pump outputis required in order to permit the compressor output to be combined withthe centrifugal pump output.

All the parts of the pump of FIGURE 8 are found in FIGURES l to 7, andin general the principle of operation is the same. Correspondingreference characters have accordingly been applied to correspondingparts with the subscript b added in each instance. No comprehensive,detailed description will be given, but attention will be confined tothe points of difference with particular emphasis upon the salientnovelty of the FIG- URE 8 form of pump.

The pump of FIGURE 8 is characterized by the fact that the blades 9b ofthe compressor rotor are made approximately as large in diameter as, or,as shown a little larger than the blades 3b of the centrifugal pumpimpeller. This is brought about by generally increasing the radialdimensions of the compressor part in proportron to the centrifugal pumppart, and by adjusting thc communicating passages slightly to maintainthe operative relation of the centrifugal pump and the comperssorpreviously described.

The desired output pressure relationship could bc brought about byrelatively increasing the speed of the compressor. For lightness,compactness and simplicity, however, the driving of the pump impellerand the compressor rotor in unison from a common shaft is foundadvantageous. In that kind of an organization the rotor diameter must beapproximately the same as the impeller diameter if the compressor outputpressure is to equal or exceed the centrifugal pump output pressure.

As before, the entrained gas and vapor are separated from the liquidfuel at the intake side of the liquid pump, are drawn olf by thecompressor, compressed, and discharged to the conduit 50h. The conduitSilb, as before, may be closed olf from communication with the conduit53h by a cover plate like the plate 56 of FIGURE 6, 1n which case theplug 9% would be removed from the internally threaded end of the conduit501) and replaced by a tube which leads to a fuel tank.

Alternatively, however, the plug Mb may be used to close the internallythreaded end of the conduit 50h, and conduit Sb may be caused to deliverto the conduit 58b through a cover plate like the cover plate 56a ofFIGURE 7. The significant feature of FIGURE 8 resides in the fact thatthe discharge pressure of the compressor is at least as great as that ofthe liquid pump. No throttling valve is required in the conduit SSb,therefore, for enabling the compressor output to be delivered to andintermingled with the liquid pump output, and none is provided.

For limiting the pressure supplied at the intake of the main fuel pump,a throttling valve may be provided at the intake of that pump, but thisvalve acts impartially upon the previously combined outputs of thecompressor and the centrifugal pump, and not upon the output of theliquid pump to the exclusion of the compressor.

The compressor of FIGURE 8 consumes relatively more power than thecompressor of FIGURES 1 to 7. The FIGURE 8 combination has a widerrange'of usefulness, however, than the combination of FIGURES 1 to 7because it can be applied in a wider range of installations, wherein arecombination of liquid pump and compressor outputs is required. y

In FIGURES 9 to 12, the invention is illustrated as embodied in acombined liquid pump .and compressor unit in which the liquid pump is oftheduplex type. Here the liquid pump is divided axiallyfinto two pumpingchambers having separate inlets but a common `outlet. The vaporsseparated in the respective intakes are separately drawn oif by therespective lobes of the compressor, the compressor having distinctintake connections to the two lobes but a common outlet from them. Thelobes of Athe compressor .are caused thus to exert their suction effectsseparately upon the vapor collection channels of the respectivecentrifugal pump chambers, caus ing each to be effectively andindependently evacuated, as pointed out in Serial No. 652,633.

The liquid pump output is throttled as in the illustrative case ofFIGURES l to and 7, and the compressor output is fed forward andcombined with the throttled liquid pump output en route to the mainengine pump.

The liquid pump of FIGURES 9 to l2 comprises body composed chiefly ofbody members 101, 1G13 and 165. The body member 101 supports the otherbody parts, being formed with a supporting flange 109 pro.- vided withbolt holes 111 through which it may be attached to the engine body. Thebody member 101 is also provided with tapped bores 113 for receivingmachine screws (not shown) through which connection may be made to aflanged fuel supply pipe (not shown).

The body member 101 is formed with a generally cylindrical openingy inwhich portions of the body memincludes a flanged end closure plate 115through which it is attached to the body member 1191 by screws 117.. Thebody member 165 similarly includes a flanged end closure plate 119through which it is secured to the body member 1111 by screws 118 Whoseshanks also pass through an attaching flange 121 of compressor headmember 123 for securing the head 123 along with Vthe plate 119 to thebody member 191. A flanged, cup-like compressor body member 125 issecured to the head 123 by screws 127.

A shaft 131 is equipped with Va splined -driving portion 133 throughwhich it may be connected to be driven by the engine itself. The shaftis supported near one end in a bearing 135 which is carried by the plate115 and near the other end in a bearing 137 which is carried by theplate 119. The bearing 137 is contined'against axial movement between ashoulder 139 of the plate 119 and a split resilient ring 141 carried bythe plate 119. A collar 143 disposed on the shaft 131 with its left facein engagement with a split resilient ring 145 that interts with theshaft, has its right face disposed to bear against the bearing 137.

To the right of the bearing 137 there are successively provided on theshaft a collar 147, a sleeve 149, the hub of compressor rotor 151, awasher 153, and a nut 155. The nut and the washer 153 clamp the rotorhub firmly against a shoulder 159 of the shaft. The collar 147, thesleeve 149, and the hub of the rotor 151 lill the space from the shaftend to the bearing 137 snugly 45 bers 103 and 105 are received. The bodymember 1&3 A'

enough to prevent end play of the shaft, but not tightly enough to causebinding or objectionable frictional resistance to rotation of the shaft.A key 157 provides a driving connection between the shaft 131 and therotor 151. y g

Between the bearings 135and 137 the shaft has Xed to it the centrifugalpump 'impeller 161. The impeller 161 comprises a central hub 16.3 whichis connected to ,the shaft 131 through a key 165. The hub is conned onthe shaft between collars 167 and 169. The collar 167 bears against ashouldered collar 171 which is integral with the shaft. The collar 169bears against a resilient split ring 173 which is interlocked with theshaft.

The spacing is such that the hub is held between the -shouldered collar171 and the split ring 173. The impeller is driven by key 165. The hub163 has integral with it a central partition ilange 175 upon which theimpeller blades 177 and 17S are mounted. I

-Liquid fuel` with entrained gas and vapor entersthe centrifugal pumpthrough an opening 179 formed in the body member111. It divides as itentersl the body, one portion going through passage 131 of the casingmember 161 andpas'sage 183 of casing member 103 to the eye of 'theimpeller at the left hand side of the partition 175, and the otherportion going through passage of casing member 1131 and passage 187 ofcasing member to the eye of the impeller at the right hand side of thepartition 175.

The two chambers of the centirfugal pump discharge the liquid in commonAto a volute passage 189 formed in the body member 191. The gases andvapors are separated from the liquid near the inner boundary of theimpeller blades, being collected. for the respective chambers 191 and.193 in annular channels 195 and 197. (See particularly FIGS. 9 and 11.)The channel 195 communicates through a passage 199 with acircumferential passage 2111 which is formed jointly between the bodymembers11 and 153. l

The channel 197 communicates through a passage 293 with a passage 265which is formed jointly by the body members 191 and 165. The channel 231is connected through passages formed in the body members 1131 and 1115with the inlet passage 233 of the one lobe of the compressor and thechannel 205 is connected through passagesformedin the body members 1111and 105, through separate inlet passage 231 connecting tothe other lobeof the compressor. Theinlet passages 231 and 233 do not communicate withone another. in this way, the lower and upper lobes of the compressorare caused to act as separate suction means for drawing off the gas andvapor from the respective centrifugal pump charnbers 191 and 193.

The compressed gases and vapors are discharged from the two lobes to acommon outlet passage 235. The passage 135 is connected through passagesto deliver the products of the compressor to a chamber 237 forrecombination with the output of the centrifugal pump after the' liquidfrom the centrifugal pump has had its pressure reduced by throttling.

The chamber 2,37, formed in the body member 191, includes a cylindricalextension 239 in which a throttling valve 241 is mounted. The throttlingvalve is designed to reduce the pressure of the liquid passing from thevolute 189 of the centrifugal `pump to the chamber 237. The valvecomprises a supporting plate 243 which, to-

gether with a cover plate 245, is clamped to the end of An opening 261formed in the cylinder 257 in line with the end of the volute 189 admitsliquid to the space 259. Normally the liquid entering the space 259flows out of this space at the forward end of the valve body throughside passages 263. The liquid which thus enters the chamber 237 bearsagainst the end of the valve body 253 and tends to force the valveupward toward a position in which communication between the space 259and the chamber 237 would be cut off. The liquid inl chamber 237 maypass through an opening 265 in the cylinder 257 tothe space whichsurrounds the bellows 249.

The interior of the bellows 249 is Vented to the atmosphere through aspace 267 which is provided between the plates 243 and 245, a port 269formed throught the plate 243, and a passage 271 formed in a sideextension of the body member 101. Atmospheric pressure, therefore,opposes the pressure of the liquid in the chamber 237, tending to holdthe passages 263 open.

A compression coil spring 273 is provided for supplev menting theresistance of the atmospheric pressure to closing of the passages 263.Means are provided for adjusting the pressure of the spring 273 againstthe body of valve 253. The spring 273 bears at one end against valvebody member 255, andat its opposite end against a flanged nut 275 whichis threaded on a screw 277. '1 he screw 277 is secured with capacity forturning, but without capacity for longitudinal movement in the coverplate 245.

A screw flange 27711 surrounds the screw snank and bears against plate245. Above the flange the screw comprises a waist portion 280, acylindrical head portion 281 and a polygonal head portion 283, the headportions being disposed to project through and beyond the cover plate245. A raised boss 285 on the face of the plate 245 surrounds the headportion 281. A locking wire 287 is disposed in a slot (not shown) of theboss 285 and extends through the head portion 281 of the .screw fornormally retaining the screw in adjusted position.

The nut 275 has a flat face that engages an inwardly extending flatfinger 289 of the cover plate 245. The finger 289 prevents rotation ofthe nut 275 so that the nut is caused to be adjusted in and out alongthe screw 277 according to the direction of turning of the screw. Toincrease the amount of pressure above atmospheric pressure which will bemaintained in the chamber 237, the nut is adjusted downward, and toreduce that pressure, the nut is adjusted upward.

The pump body member 101 also includes a passage 291, which is incommunication with the inlet of the main engine pump, which in turn alsocommunicates with the discharge chamber of the pump by means of thecheck valve 293. This check valve serves as a by-pass means to allowfuel to pass through the pump casing from its inlet to its dischargewith minimum pressure drop when the pump is for any reason renderedinoperative.

The valve 293 includes a stern 297 which is guided in a bare 299 formedin a plate 301. The plate 301 is secured to the body 101 by screws 303.The bore 299 is formed in an axially elongated central portion of theplate y, l,

301. The bore contains in its inner end a compression coil spring 305,which urges the valve 293 toward its seat with predetermined force. Thevalve normally closes the passage 307 through which the passage 291 andthe volute 189 communicate, being urged closed by the prev determinedforce of the spring 30S and also being held closed by the pressuredifference normally maintained by the pump while operating between thedischarge pressure developed in the volute 189 and the suction pressureof its inlet and existing in chamber 307. Upon stoppage of the pump, dueto anyfailure of its drive system or in the pump itself, the main enginepump can still pump fuel through the booster pump by overcoming theslight pressure `difference caused by the spring 305, thus permittingvvalve 293 to open and fuel to pass with a minimum pressure drop throughthe pump structure.

` i The pumped liquid, whether or not combined with the .compressoroutput is discharged from the chamber 237 'ments of my invention. I donot wish, however, to be confined to the embodiments shown, but what Idesire to cover by letters patent is set forth in the appended claims.

I claim:

l. A liquid pump for pumping liquid at or near its boiling pointcomprising a housing including a liquid pump chamber portion havingcentral inlets at each end thereof and an intermediate annular dischargepassage, an outlet passage for said liquid pump communicating with saidannular discharge passage, a rotatable main shaft centrally mounted insaid housing in said liquid pumping chamber portion, a liquid impellerof the duplex radial type affixed to said shaft for rotation therewith,a liquid ring compressor chamber portion defined within vthe interior ofsaid housing in alignment with said pumping chamber portion, said mainshaft extending therethrough, a compressor rotor affixed to said shaftin said compressor chamber portion, said compressor rotor being of lessdiameter than said impeller rotor to develop a discharge pressure lessthan that of said liquid pumping chamber portion, vapor and gas inletmeans for said liquid ring compressor chamber portion including aninternal passage in said housing connecting said compressor chamberportion inlet means with said liquid pumping chamber portion at thelocation of each of said spaced inlets to continuously remove gas andliquid having entrained vapor from said liquid pumping portion, means torotate said main shaft, a pressure reducing valve interposed in saidoutlet passage for said liquid pumping portion, said valve includingpressure responsive means connected to the ambient pressure, andcooperating pressure responsive means in fluid communication andresponsive to the discharge of the centrifugal liquid pump portion, saidlast-named means acting as a control to regulate the liquid dischargepressure in conformity with the discharge pressure of the compressorportion and a discharge passage dened in said housing for condensedliquid and vapor connecting said compressor chamber portion and saidliquid outlet passage at a location downstream of said valve.

2. A liquid pump according to claim 1 wherein said liquid ringcompressor portion includes two lobed portions and a separate inletfeeding each of said lobed portions, each of said inlets being connectedto said liquid pumping chamber portion in the vicinity of a respectiveone of said liquid pumping chamber inlets.

3. A liquid pump according to claim l including, fluid by-pass meansconnecting said liquid pump chamber portion inlets and said condensedliquid and vapor discharge passage, and check valve means i'n saidby-pass nieans to allow liquid to pass through the pump from its inletto its outlet with minimum pressure drop when the pump is inoperative.

4. A liquid pump for pumping liquid at or near its boiling pointcomprising a housing including, a liquid pumping chamber portion havingcentral spaced inlets at each end thereof and an intermediate annularvolute discharge passage, an outlet passage for said liquid pumpcommunicating with said volute discharge passage, a rotatable main shaftcentrally mounted in said housing in said liquid pumping chamberportion, a liquid impeller of the duplex radial type affixed to saidshaft for rotation therewith, a liquid ring compressor chamber portiondefined within the interior of said housing including a rotor affixed tosaid shaft and arranged in said compressor chamber portion, means torotate said main shaft, vapor and gas inlet means for said liquid ringcompressor chamber portion including an internal passage in said housingconnecting said compressor cham- 13 ber portion inlet means with saidliquid pumping chamber portion at the location of each of said spacedinlets to continuously remove gas and liquid having entrained vapor fromsaid liquid pumping portion, a discharge passage delined in said housingfor condensed liquid and vapor connecting said compressor chamberportion and said outlet passage, and means for reducing the pressure ofthe liquid in said outlet passage prior to its being combined with thecondensed liquid and vapor from said discharge passage, said lastmentioned pressure reducing means including a throttle valve, andactuation means in iuid communication with the liquid in the outletpassage and with atmospheric pressure for positioning said throttlevalve in proportion to the pressure balance between the ambientatmospheric pressure and the pressure of the liquid in said outletpassage whereby said cornpressor chamber portion output is mixed withthe liquid discharge in said outlet passage at substantially the samep'ifessures.

5. A liquid pump according to claim 4 including, iluid by-pass meansconnecting said liquid pump chamber portion inlets and said condensedliquid and Vapor discharge passage and check valve means in said by-passmeans to allow liquid to pass through the pump from its inlet to itsdischarge with minimum pressure drop when the pump is inoperative.

References Cited in the tile of this patent UNITED STATES PATENTS2,461,865 Adams Feb. 15, 1949 2,553,066 Southern May 15, 1951 2,612,844Grise Oct. 7, 1952 2,666,393' Troeger et al Ian. 19, 1954 FOREGN PATENTS682,295 France May 26, 1930 511,305 Great Britain Aug. 16, 1939 97,078Sweden Oct. 10, 1939

1. A LIQUID PUMP FOR PUMPING LIQUID AT OR NEAR ITS BOILING POINTCOMPRISING A HOUSING INCLUDING A LIQUID PUMP CHAMBER PORTION HAVINGCENTRAL INLETS AT EACH END THEREOF AND AN INTERMEDIATE ANNULAR DISCHARGEPASSAGE, AN OUTLET PASSAGE FOR SAID LIQUID PUMP COMMUNICATING WITH SAIDANNULAR DISCHARGE PASSAGE, A ROTATABLE MAIN SHAFT CENTRALLY MOUNTED INSAID HOUSING IN SAID LIQUID PUMPING CHAMBER PORTION, A LIQUID IMPELLEROF THE DUPLEX RADIAL TYPE AFFIXED TO SAID SHAFT FOR ROTATION THEREWITH,A LIQUID RING COMPRESSOR CHAMBER PORTION DEFINED WITHIN THE INTERIOR OFSAID HOUSING IN ALIGNMENT WITH SAID PUMPING CHAMBER PORTION, SAID MAINSHAFT EXTENDING THERETHROUGH A COMPRESSOR ROTOR AFFIXED TO SAID SHAFT INSAID COMPRESSOR CHAMBER PORTION, SAID COMPRESSOR ROTOR BEING OF LESSDIAMETER THAN SAID IMPELLER ROTOR TO DEVELOP A DISCHARGE PRESSURE LESSTHAN THAT OF SAID LIQUID PUMPING CHAMBER PORTION VAPOR AND GAS INLETMEANS FOR SAID LIQUID RING COMPRESSOR CHAMBER PORTION INCLUDING ANINTERNAL PASSAGE IN SAID HOUSING CONNECTING SAID COMPRESSOR CHAMBERPORTION INLET MEANS WITH SAID LIQUID PUMPING CHAMBER PORTION AT THELOCATION OF EACH OF SAID SPACED INLETS TO CONTINUOUSLY REMOVE GAS ANDLIQUID HAVING ENTRAINED VAPOR FROM SAID LIQUID PUMPING PORTION, MEANS TOROTATE SAID MAIN SHAFT, A PRESSURE REDUCING VALVE INTERPOSED IN SAIDOUTLET PASSAGE FOR SAID LIQUID PUMPING POR-